Catheter guide wires (guidewires) have been used to “lead” or “guide” catheters to desired target locations in animal or human anatomy. This may be done via a body's lumen, for example such as traversing luminal spaces defined by the vasculature to the target location. Typical guidewires may be from about 135 centimeters to 195 centimeters in length, and have been made from two primary components—a stainless steel solid core wire, and a platinum alloy coil spring. The core wire may be tapered on the distal end to increase its flexibility. The coil spring may be soldered to the core wire at its distal end and at a point where the inside diameter of the coil spring matches the outside diameter of the core wire. Platinum has been used for the coil spring because it provides good fluoroscopic or other radiological imaging during navigation of the guidewire in the body, and it is generally biocompatible. The coil spring may also provide softness for the tip of the guidewire to reduce the likelihood of unwanted puncture of a Luminal wall or the damaging of this or other anatomy.
As mentioned, navigation of a guidewire through the anatomy may be achieved with the assistance of radiographic imaging. This may be done by introducing contrast media into the body lumen being traversed and viewing the guidewire in the body lumen using X-ray fluoroscopy or other comparable methods. The guidewire may be provided with a tip that is curved or bent to a desired angle so as to deviate laterally a short distance. By rotation of the wire, the tip can be made to deviate in a selected direction from an axis of the guidewire about which it rotates. In some devices the catheter enables introduction of contrast media at the location of the distal tip to enable the visualization of a Luminal space being traversed by the catheter and guidewire. Visualization may be by fluoroscope, for example, or another device.
The guidewire or catheter may be introduced into a Luminal space, comprising for example a vessel or duct, and advanced therethrough until the guidewire tip reaches a desired vessel or luminal branch. The user may then twist the proximal end of the guidewire so as to rotate and point the curved distal tip into the desired branch so that the device may be advanced farther into the anatomy via the luminal branch. The catheter may be advanced over the guidewire to follow or track the wire. This procedure may be repeated as needed to guide the wire and overlying catheter to the desired target location. Once the catheter has been advanced to the desired location, the guidewire may be withdrawn, depending upon the therapy to be performed. Oftentimes, such as in the case of balloon angioplasty, the guidewire may be left in place during the procedure and may be used to exchange catheters.
From this description, it will be apparent that a guidewire having very low resistance to flexure yet relatively high torsional strength may be most desirable. As the guidewire is advanced into the anatomy, internal resistance from the typically numerous turns, and surface contact, decreases the ability to advance the guidewire further. This, in turn, may lead to a more difficult and prolonged procedure, or, more seriously, failure to access the desired anatomy and thus a failed procedure. A guidewire with high flexibility helps overcome the problems created by internal resistance. However, if the guidewire does not also have good torque characteristics (torsional stiffness), the user will not be able to rotate the distal tip of the guidewire as required by twisting the proximal end. Prior art catheter guidewires that are flexible in bending typically have very poor torsion transmission characteristics or torsional stiffness. The result may be that the end of the guidewire flops around, but cannot easily be turned or rotated within a catheter or vessel.